Very often some of the most interesting ideas are the hardest to describe, perhaps until we find a whole new name for them. And here's another in that vein; a fascinating campaign meets game meets mobile mashup from the brains behind Moblog.

It started with an experiment by Moblog co-founder Alfie Dennen in using Google Maps to plot real-world objects that would create an image on the map; his prototype was an eye laid out on the football pitch behind his house. GPS drawing in itself isn't new, but Dennen wanted to use this idea for some greater good.

I don't want to give away too much about the project, but if I share some of the ingredients you'll get a taste of it.

Very late on Sunday night, Dennen and volunteers will be trekking around a mile-square chunk of central London laying out 43 objects in set locations. The objects are quite interesting objects in themselves, and the first to find them will be able to keep them. The objects include some essential details that will allow the player to plot the object on the project's Google Map, with mashery goodness provided by HomeMade Digital. All of those objects will, collectively, form part of a greater whole...

And this is all knitted together around the superb work of American photojournalist and war photographer James Nachtwey, who has created the campaign site XDRTB.org. I can't possibly not tell you about the campaign itself, as that's the whole point; it's to promote awareness of 'extremely drug-resistant tuberculosis'. Though you'll have heard of tuberculosis, you might not know that it still kills 1.7m people a year and kills more HIV sufferers than any other disease. So the campaign is already working.